I just bought a variable regulated dc power supply for testing purposes and the fan is very noisy. I would like to use the arduino platform to build a fan controller for it so if I am drawing a small load the fan is either off or at a lower speed until the temperature requires a faster rpm.

Would any of the existing pc fan controller circuits etc already made suit my purposes?It will probably be pid control I assume from what I have read so far.

If anyone has a project suggestion for me or could point me to a good post on the subject please let me know.

Sorry about that. It seems to be a standard 12v case fan. Will measure it shortly but I think its a standard 60 or 80 mm.there is just the one 12v connector coming off the board. There is also a thermistor I am guessing attached to the heatsink but I cannot read what type it is due to the positioning.

As the fan comes on full time I am guessing that the circuit for reading the temperature etc is not working and therefore I should be able to attach the Arduino circuit to the existing 12v connector and have it powered constantly.

I am guessing I could just get a 1 wire device like the ds18b20 and add either a voltage divider or a voltage regulator to provide 5v to the arduino and the rest will be done in software.

I am not sure what the circuit is, I think it is pic based that drives the temperature controller.It seems to be a common fault because the person who suggested I buy one and recommended it to me has the same thing and has devised his own board, I wanted to make something non pic based though because I never had much luck with those microcontrollers.I understand Arduino a little more.

I was planning on making it variable based on the load if possible.

Just reading up on PID control but I am nowhere near getting my head around it yet.

Just reading up on PID control but I am nowhere near getting my head around it yet.

Given the constraints (very fast acting control point; slowly changing process variable) I suspect you can get good results with a very basic algorithm: Temperature a bit too high? Speed up the fan just a bit. Temperature way too high? Set the fan speed to maximum. Temperature going down? Slow down the fan just a bit. Temperature normal? Stop the fan. Delay for a short time. Repeat.

If you really want to get fancy, measure the power output (or input) and try your hand at predictive control.